Transcript Slide 1

NGC 2110 Spectroscopy
Dan Evans (Harvard), Julia Lee (Harvard), Jane Turner (UMBC/GSFC),
Kim Weaver (GSFC), Herman Marshall (MIT)
NGC 2110 Spectroscopy
Fe Kα Lines and Reflection: AGN Geometry
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The Fe Kα line complex in general
consists of a narrow line core,
possibly accompanied by broadened
emission
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What is the origin of the broad
emission?
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Relativistically blurred diskline?
Compton shoulder?
Broad line region?
Unmodeled absorption?
If we can deconvolve the
contributions from the two, we can
probe AGN geometry
Vital to treat direct+reflected
continuum and absorption effects
self-consistently
Diskline?
Compton
shoulder?
Complex
absorption?
NGC 3783 (Yaqoob et al. 2005)
Nearby (z=0.0076, DL=33 Mpc) NELG
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Historical subclass of Seyferts with narrow
(<600 km/s) optical lines (Sy 2-like) but much
stronger hard X-ray emission (Sy 1-like)
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Flat X-ray spectra may imply they dominate
XRB at low energies (e.g. Iwasawa et al. 1997)
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Transitional between Sy 1 and Sy 2? (Lawrence
& Elvis 1982)
ASCA, BeppoSAX, etc.  2-10 keV X-ray
spectrum is very flat (Г=1.4)
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Accompanied by moderate absorption
(NH=3x1022 cm-2)
ASCA Fe K complex hard to interpret
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Diskline, either oriented at intermediate angles
to l.o.s. (Weaver & Reynolds 1998) or nearly
face-on (Turner et al. 1998)
NGC 2110 Spectroscopy
NGC 2110
NGC 2110 Spectroscopy
NGC 2110 was observed with Chandra
for a total of 250 ks and XMM-Newton
for 60 ks. An initial analysis showed
variability in flux only, and so the
continuum spectra were analyzed jointly.
Instrument
Date
Exposure (ks)
HETGS
2001 Dec 19
35
HETGS
2001 Dec 20
80
HETGS
2001 Dec 22
35
HETGS
2003 Mar 05
100
EPIC/RGS
2003 Mar 05
60
2003 Mar
HETGS light curve
2001 Dec
NGC 2110 Spectroscopy
Chandra and XMM-Newton
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Initial fit with single, moderately
absorbed power law (NH=3x1022 cm2, Г=1.4)
Soft excess seen below 2 keV
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Significant improvement in fit with
the addition of a lightly absorbed
(NH=7x1020 cm-2) power law
(Гsoft=Гhard)
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Still very flat photon index (Г=1.4),
but…
XMM pn
MEG
XMM pn
MEG
NGC 2110 Spectroscopy
Continuum Fitting
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Insufficient opacity at Si K and Fe K
edges
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Improvement in the fit with the
additional edges
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Does this imply an extra absorber?
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Significant improvement with a 3x
partially covered power law
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HEG
XMM pn
Photon index rises to Г=1.74±0.05 
consistent with canonical values in
Seyferts
MEG
HEG
No evidence for ionized absorption
in HETGS data
Component
Column density (cm-2)
Covering fraction
NH,1
1.6x1023
32%
NH,2
2.8x1022
65%
NH,3
7.7x1020
3%
NGC 2110 Spectroscopy
Continuum Fitting
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Chandra HETGS best suited to probe
narrow lines
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Neutral fluorescent Kα lines detected
from Si, S, Ar, Ca, Fe
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Narrow Fe Kα and Si Kα line cores just
resolved with HETGS
Line
Energy
(keV)
Width
(km s-1)
Equivalent
width (eV)
Fe Kα
6.397±0.007 900±500
80±30
Si Kα
1.740±0.002 600±400
6±2
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Distant, neutral fluorescing region
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No evidence for diskline
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Marginal (2.5σ) evidence for v. slight
broadened base of Fe Kα
HEG
HEG
NGC 2110 Spectroscopy
Fluorescent Line Diagnostics
NGC 2110 Spectroscopy
Reflection
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Self-consistent treatment of reflection
(i.e., lines+pexrav continuum)
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No change in fit parameters
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Suzaku provides vital constraints on
strength of reflection
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Stringent limit of R<0.1 (Reeves et al.
2006; Okajima et al. 2007)
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NGC 2110 is one of the few Seyferts
with no evidence for disk reflection,
nor complex absorption
Suzaku – NGC 2110 (Reeves et al. 2006)
NGC 2110 Spectroscopy
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Excellent spatial agreement between
X-ray and [OIII] (Evans et al. 2006)
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Both clearly offset from radio, but
extend along similar p.a.
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X-ray & [OIII] emission influenced by,
but not directly associated with, radio
jet?
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ACIS X-ray spectrum modeled by, e.g.,
two thermal plasma models (kT1=0.3
keV; kT2=5 keV)
2’’=320 pc
Chandra (0.5-1.5 keV) / VLA / HST [OIII]
NGC 2110 Spectroscopy
Multiwavelength Imaging
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Evans et al. (2006) considered 3 mechanisms for producing the environment:
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Shock-heating by the radio jet
Electron-scattered nuclear radiation
Photoionization by the AGN
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High-resolution grating
spectroscopy can in principle
distinguish between these models
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Tentative evidence for O VIII Ly α,
as well as the O VIII RRC feature
first reported by Guainazzi &
Bianchi (2006)
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Photoionization and collisional ionization processes both important?
NGC 2110 Spectroscopy
Gratings Spectrum
NGC 2110 Spectroscopy
ASCA, BeppoSAX, etc. found
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Flat (Г=1.4) 2-10 keV spectrum
Moderate absorption (NH=3x1022 cm-2)
Diskline emission, either face-on or at
intermediate angles
Component
Column density (cm-2)
Covering fraction
NH,1
1.6x1023
32%
NH,2
2.8x1022
65%
NH,3
7.7x1020
3%
Chandra, XMM-Newton (and Suzaku –
Okajima et al. 2007)
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Compton-thin partial-coverer model
Photon index 1.7-1.8
No evidence for ionized absorption
Marginally resolved (900±500 km s-1) Fe Kα
line core
No evidence for disk reflection
Multiwavelength imaging + HETGS evidence
for (weak) ionized emission  extended
circumnuclear environment is photoionized
or collisionally ionized?
2’’=320 pc
NGC 2110 Spectroscopy
Recap
Consistent with an origin in a Compton-thin, distant (> 1pc) neutral absorber
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Orientation consistent with edge-on view
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Steepening of photon index using multiple partial-coverer model  NELGs do
not have significantly flatter spectra w.r.t. Seyfert 1, 2?
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No disk reflection, unlike other Compton-thin Seyferts observed with Suzaku
(Reeves et al. 2006)
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Vital to treat absorption and reflection effects in a self-consistent manner in
order to evaluate AGN geometry
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High spatial and spectral resolution, together with high effective area, are key
to determining the spatial distribution and energetics (collisional vs.
photoionization) of circumnuclear environments in AGN
NGC 2110 Spectroscopy
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